The present application relates to the sensors and, more particularly, to a high voltage supply for increasing current through a light source in an optical sensor system.
Optical sensor systems may be used to locate and/or image an object by detecting light reflected from the object. Such systems may include a light source that transmits light toward an object and a detector for detecting portions of the transmitted light reflected by the object. A characteristic of the reflected light may be analyzed by the sensor system to determine the distance to an object and/or to generate an electronic image of the object.
In one example, such a system may include a light source, such as one or more light emitting diodes (LEDs), configured to transmit modulated infrared light (IR), i.e. IR light that is rapidly turned on and off. The detector may receive the reflected light and calculate the phase shift imparted by reflection of the light back to the senor. The time of flight of the received light may be calculated from the phase shift and distance to various points in the sensor field of view may be calculated by multiplying the time of flight and the velocity of the signal in the transmission medium. By providing an array of receiving pixels in the detector, the distance signals associated with light received at each pixel may be mapped to generate a three-dimensional electronic image of the field of view.
The manner of modulation of the light source in such systems is a factor in system performance. To achieve useful and accurate imaging, it is desirable to modulate the light source at a high frequency, e.g. 40 MHz. In addition, it is desirable in such systems to modulate the light source with high efficiency and reliability, while maintaining reasonable cost of manufacture and a relatively small package size.
In an embodiment, there is provided a light source circuit for an optical sensor system. The light source circuit includes: a power supply to provide a regulated direct current (DC) voltage output; a light source; a current source coupled to the power supply and the light source to receive the regulated DC voltage output and to provide a current output; a first switch, the first switch being configured to allow the current output to the light source from the current source when the first switch is closed and to prevent the current output to the light source when the first switch is open; a high voltage supply circuit coupled to the light source to provide a high voltage output; and a second switch, the second switch being configured to connect the high voltage output to the light source from the high voltage supply when the second switch is closed and to disconnect the high voltage output from the light source when the second switch is open.
In a related embodiment, the circuit may further include a drive circuit to open and close the second switch, the drive circuit being configured to close the second switch at the start of an on time for the light source to connect the high voltage output to the light source and to open the second switch during a remainder of the on time of the light source to allow the current source to provide the current output to the light source. In another related embodiment, the circuit may further include a drive circuit to open and close the first and second switches at a predetermined frequency. In a further related embodiment, the predetermined frequency may be about 40 MHz.
In yet another related embodiment, the circuit may further include a diode coupled between the current source and the light source, the diode being configured to conduct to provide the current output to the light source only when the first switch is closed and the second switch is open. In still another related embodiment, the current source may include: an inductor connected in series with a resistor; and a diode coupled in parallel with the inductor and resistor; and wherein the current source is configured to provided the current output through the inductor to the light source when the first switch is closed and divert current through the inductor to the diode when the first switch is open. In a further related embodiment, the current source may include a current monitor coupled to the resistor and configured to provide the current feedback.
In still yet another related embodiment, the light source may include a plurality of series connected light emitting diodes.
In another embodiment, there is provided an optical sensor system. The optical sensor system includes: a controller; a light source circuit coupled to the controller to drive a light source in response to control signals from the controller, the light source circuit includes: a power supply to provide a regulated direct current (DC) voltage output; a current source coupled to the power supply and the light source to receive the regulated DC voltage output and to provide a current output; a first switch, the first switch being configured to allow the current output to the light source from the current source when the first switch is closed and to prevent the current output to the light source when the first switch is open; a high voltage supply circuit coupled to the light source to provide a high voltage output; and a second switch, the second switch being configured to connect the high voltage output to the light source from the high voltage supply when the second switch is closed and to disconnect the high voltage output from the light source when the second switch is open; transmission optics to direct light from the light source toward an object; receiver optics to receive light reflected from the object; and detector circuits to convert the reflected light to one or more electrical signals; wherein the controller is configured to provide a data signal output representative of a distance to at least one point on the object in response to the one or more electrical signals.
In a related embodiment, the optical sensor system may further include a drive circuit to open and close the second switch, the drive circuit being configured to close the second switch at the start of an on time for the light source to connect the high voltage output to the light source and to open the second switch during a remainder of the on time of the light source to allow the current source to provide the current output to the light source. In a further related embodiment, the optical sensor system may further include a diode coupled between the current source and the light source, the diode being configured to conduct to provide the current output to the light source only when the first switch is closed and the second switch is open.
In another related embodiment, the optical sensor system may further include a drive circuit to open and close the first and second switches at a predetermined frequency. In a further related embodiment, the predetermined frequency may be about 40 MHz. In still another related embodiment, the current source may include: an inductor connected in series with a resistor; and a diode coupled in parallel with the inductor and resistor; and wherein the current source is configured to provided the current output through the inductor to the light source when the first switch is closed and divert current through the inductor to the diode when the first switch is open. In a further related embodiment, the current source may include a current monitor coupled to the resistor and configured to provide the current feedback.
In yet another related embodiment, the light source may include a plurality of series connected light emitting diodes.
In yet another embodiment, there is provided a method of providing current to a light source in an optical sensor system. The method includes: connecting an initial voltage across the light source from a high voltage supply circuit during a start of an on time for the light source; disconnecting the initial voltage from the light source before the end of the on time for the light source; and providing current through a current source to the light source when the initial voltage is disconnected and for a remainder of the on time for the light source. In a related embodiment, connecting may include connecting an initial voltage across a plurality of series connected light emitting diodes from a high voltage supply circuit during a start of an on time for the plurality of series connected light emitting diodes; and disconnecting may include: disconnecting the initial voltage from the plurality of series connected light emitting diodes before the end of the on time for the plurality of series connected light emitting diodes; and providing may include: providing current through a current source to the plurality of series connected light emitting diodes when the initial voltage is disconnected and for a remainder of the on time for the plurality of series connected light emitting diodes.
The foregoing and other objects, features and advantages disclosed herein will be apparent from the following description of particular embodiments disclosed herein, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles disclosed herein.
Those of ordinary skilled in the art will recognize that the optical sensor system 100 has been depicted in highly simplified form for ease of explanation. The optical sensor system 100 shown in
The light source circuits 112 may include known circuitry for driving the light source in response to control outputs from the controller/processing circuits 110, and may include circuitry consistent with the present disclosure. The transmission optics 114 may include known optical components for directing light output from the light source to provide a system field of view encompassing the object(s) of interest. The receiver optics 116 may include known optical components for receiving light reflected from the object of interest and directing the received light to the detector circuits 118. The detector circuits 118 may include known light detectors, e.g. arranged in an array of pixels, for converting the received light into electrical signals provided to the control/processing circuits 110. The detector circuits 118 may, for example, be any of the detector circuits commercially available from Canesta, Inc. of Sunnyvale, Calif. The control processing circuits 110 may calculate distance to various points on the object and within the system field of view, e.g. using phase shift in the received light to calculate time of flight and distance, to provide the data output indicating distance to the object and/or mapping the object to provide a three-dimensional image thereof.
The power supply 202 may take any known configuration for receiving an input voltage from an input voltage source 212 and providing a regulated direct current (DC) voltage output. The input voltage source 212 may be, as is shown in
The current source 204 may provide a constant current to the one or more light sources 206 to energize the light sources when the switch S1 is closed by the driver circuits 210. The switch S1 is illustrated in diagrammatic form for ease of explanation, but may take any of a variety of configurations known to those of ordinary skill in the art. For example, the switch S1 may be a transistor configuration that conducts current under the control of the driver circuit output.
The driver circuits 210 may be configured to open and close the switch S1 at a predetermined frequency under the control of control signals 214 from the controller/processing circuits 110. In some embodiments, for example, the driver circuits 210 may open and close the switch S1 at a frequency of about 40 MHz. The current source 204 may thus provide a driving current to the one or more light sources 206 at the predetermined frequency for modulating the one or more light sources 206, i.e. turning the one or more light sources 206 on and off.
The high voltage supply circuit 208 may be coupled to the light source through the switch S2. The switch S2 may be closed by the driver circuits 210 under the control of control signals from the controller/processing circuits 110 during the start of the “on” time for the one or more light sources 206. A high voltage, i.e. higher than the output voltage of the power supply 202, may be coupled from the power supply 202 to the high voltage supply circuit 208, e.g. by path 218, and the high voltage supply circuit 208 may provide a high voltage output Vh across the one or more light sources 206. In some embodiments, for example, the high voltage output Vh may be about 18V, whereas the regulated DC output of the power supply 202 may be about 10V.
The high voltage supply circuit 208 may thus increase the voltage across the one or more light sources 206 to a higher voltage than can be established by the current source 204 to overcome the parasitic inductance in the one or more light sources 206 and decrease the rise time of the current through the one or more light sources 106. After the start of the “on” time for the one or more light sources 106 the switch S2 may open to disconnect the high voltage supply circuit 208 from the one or more light sources 106, and the switch S1 may be closed to allow the current source 204 to drive the one or more light sources 106 through the rest of the “on” time. The switch S2 is illustrated in diagrammatic form for ease of explanation, but may take any of a variety of configurations known to those of ordinary skill in the art. For example, the switch S2 may be a transistor configuration that conducts current under the control of the output of the driver circuits 210.
As shown, the regulated DC output Vs of the power supply 202 may be coupled to the input of the current source 204a at the resistor R1. The driver circuits 210 may open and close the switch S1 at a high frequency, e.g. 40 MHz. When the switch S1 is closed, a current Is flows through the series combination of the resistor R1 and the inductor L1, and to the one or more light sources 206 to energize the light source. The inductor L1 thus establishes a constant current source and limits the current Is through the one or more light sources 206 when the switch S1 is closed. When the switch S1 is open, however, no current flows through the one or more light sources 206, and the current IL through the inductor L1 is diverted through the diode D1 to maintain current through the inductor L1.
As shown, the current monitor 304 may be coupled across the resistor R1 for sensing the voltage drop across resistor R1. The current monitor 304 may take any configuration known to those of ordinary skill in the art. In some embodiments, for example, the current monitor 304 may be configured using a current shunt monitor available from Texas Instruments® under model number INA138. The current monitor 304 may provide a feedback output to the power supply 202, e.g. through the diode D2.
In response to the feedback from the current monitor 304 and during the time when the switch S1 is closed, the power supply 202 may be configured to adjust the supply voltage Vs to a voltage that will allow the inductor L1 to recharge. In some embodiments, the feedback path 302 maybe coupled to a voltage feedback path of the power supply 202 to provide a constant current control loop that takes control away from the voltage control loop during the time when the switch S1 is closed, i.e. the “on” time for the one or more light sources 206. A variety of configurations for providing an adjustable supply voltage in response to the current monitor feedback are well-known to those of ordinary skill in the art. In some embodiments, for example, the power supply 202 may be configured as a known converter, e.g. a SEPIC converter, and a known converter controller, e.g. a SEPIC controller configured to control the converter output in response to the current monitor feedback. A constant current may thus be established through the inductor L1 when the switch S1 is closed, i.e. when the one or more light sources 206 is/are “on” and emitting light.
Again, the high voltage supply circuit 208 is coupled to the one or more light sources 206 through the switch S2. The switch S2 may be closed by the driver circuits 210 under the control of control signals from the controller/processing circuits 118 during the start of the “on” time for the one or more light sources 206. When the voltage output of the high voltage supply circuit 208 is coupled to the one or more light sources 206, i.e. the switch S2 is closed, a diode D7 blocks the high voltage output of the high voltage supply circuit 208 from the current source 204a. After the start of the “on” time for the one or more light sources 206, the switch S2 may open to disconnect the high voltage supply circuit 208 from the one or more light sources 206. The diode D7 may then conduct and the current source 204a may drive the one or more light sources 206 through the rest of the “on” time.
As shown in
In
Those of ordinary skill in the art will recognize that a high voltage supply may be provided in a variety of configurations.
A high voltage input is coupled to the source of the first MOSFET Q1 from a node in the power supply that has a higher voltage than the output voltage of the power supply. In some embodiments, for example, the drain of the power MOSFET in a SEPIC converter implementing a model number LTC1871® SEPIC converter controller available from Linear Technology Corporation may be coupled to the source of the first MOSFET Q1. The gate of the first MOSFET Q1 may be coupled to the drive circuit. The drive circuit may provide a square wave signal to the gate of the first MOSFET Q1 for causing the first MOSFET Q1 and the second MOSFET Q2 to conduct periodically, i.e. to open and close the switch S2a as described above. When the first MOSFET Q1 and the second MOSFET Q2 conduct, the high voltage across a resistor R2 and a capacitor C1 is provided across the light source.
Unless otherwise stated, use of the word “substantially” may be construed to include a precise relationship, condition, arrangement, orientation, and/or other characteristic, and deviations thereof as understood by one of ordinary skill in the art, to the extent that such deviations do not materially affect the disclosed methods and systems.
Throughout the entirety of the present disclosure, use of the articles “a” or “an” to modify a noun may be understood to be used for convenience and to include one, or more than one, of the modified noun, unless otherwise specifically stated.
Elements, components, modules, and/or parts thereof that are described and/or otherwise portrayed through the figures to communicate with, be associated with, and/or be based on, something else, may be understood to so communicate, be associated with, and or be based on in a direct and/or indirect manner, unless otherwise stipulated herein.
Although the methods and systems have been described relative to a specific embodiment thereof, they are not so limited. Obviously many modifications and variations may become apparent in light of the above teachings. Many additional changes in the details, materials, and arrangement of parts, herein described and illustrated, may be made by those skilled in the art.
This application claims priority from the following commonly owned U.S. Provisional Patent Applications: Ser. No. 61/165,171, Ser. No. 61/165,181, Ser. No. 61/165,388, and Ser. No. 61/165,159, all of which were filed on Mar. 31, 2009. This application is related to the following commonly-owned applications: U.S. Utility patent application Ser. No. 12/652,083, entitled “CURRENT SOURCE TO DRIVE A LIGHT SOURCE IN AN OPTICAL SENSOR SYSTEM”; U.S. Utility patent application Ser. No. 12/652,087, entitled “DUAL VOLTAGE AND CURRENT CONTROL FEEDBACK LOOP FOR AN OPTICAL SENSOR SYSTEM”; and U.S. Utility patent application Ser. No. 12/652,087, entitled “OPTICAL SENSOR SYSTEM INCLUDING SERIES CONNECTED LIGHT EMITTING DIODES”; all filed on Jan. 5, 2010, and all of which are hereby incorporated by reference.
Number | Name | Date | Kind |
---|---|---|---|
4017847 | Burford et al. | Apr 1977 | A |
4743897 | Perez | May 1988 | A |
5365148 | Mallon et al. | Nov 1994 | A |
RE36789 | Mandel et al. | Jul 2000 | E |
6584283 | Gabello et al. | Jun 2003 | B2 |
7202641 | Claessens et al. | Apr 2007 | B2 |
20020047642 | Miyagawa | Apr 2002 | A1 |
20040090403 | Huang | May 2004 | A1 |
20040251854 | Matsuda et al. | Dec 2004 | A1 |
20050134198 | Crandall et al. | Jun 2005 | A1 |
20050207196 | Holmes et al. | Sep 2005 | A1 |
20050243022 | Negru | Nov 2005 | A1 |
20060038803 | Miller et al. | Feb 2006 | A1 |
20070024215 | Garbowicz et al. | Feb 2007 | A1 |
20070057936 | Lee et al. | Mar 2007 | A1 |
20080093997 | Chen et al. | Apr 2008 | A1 |
20080174929 | Shen et al. | Jul 2008 | A1 |
20080191642 | Slot et al. | Aug 2008 | A1 |
20080304043 | Benz et al. | Dec 2008 | A1 |
20090058323 | Yang | Mar 2009 | A1 |
20090079363 | Ghoman et al. | Mar 2009 | A1 |
20090267534 | Godbole et al. | Oct 2009 | A1 |
20100164405 | Tobey et al. | Jul 2010 | A1 |
Number | Date | Country |
---|---|---|
2004-057924 | Jul 2004 | WO |
Entry |
---|
International Search Report, completed Sep. 16, 2010, pp. 1-3, Korean Intellectual Property Office, Daejeon, Republic of Korea. |
Written Opinion of the International Searching Authority, completed Sep. 16, 2010, pp. 1-4, Korean Intellectual Property Office, Daejeon, Republic of Korea. |
Number | Date | Country | |
---|---|---|---|
20100243897 A1 | Sep 2010 | US |
Number | Date | Country | |
---|---|---|---|
61165171 | Mar 2009 | US | |
61165181 | Mar 2009 | US | |
61165388 | Mar 2009 | US | |
61165159 | Mar 2009 | US |